Technical Field
The present application relates to an illumination and imaging technology, and in particular, to a telecentric illumination and photographing system for detection of marine microscopic organisms, providing illumination to detection of marine microscopic organisms.
Related Arts
With the development of scientific researches, it is found that data such as existence and growth of microscopic organisms in water system environments such as oceans, lakes, and rivers, ingredients of metabolins, and water-soluble gas ingredients all closely and accurately reflects a condition of a local environment and is closely linked with a living environment of people. However, there are quite a lot of technical problems for technical means of researching microscopic organisms because sizes and dimensions of microscopic organisms are mostly at the micrometer scale, especially in a relatively turbid water body and in a water body of a sludge mixture.
When imaging microscopic organisms, a general illumination light source and a photographing camera have problems such as scattering, light interference, and non-uniform imaging illuminance, causing many adverse effects on observation of the microscopic organisms. For example, scattering results in vague imaging and low contrast, coherent stripes are formed and an alternation of bright and dark areas of a part of an image surface is caused due to light interference, and non-uniform imaging illuminance affects overall observation of imaging.
In addition, a high-power light emitting diode (LED) system for illumination also needs a better drive, and available drives mainly include three types, that is, a current-limiting resistor, a linear voltage regulator, and a switching converter. A current-limiting resistor solution is applicable to an application scenario with low efficiency and has an extremely high requirement for efficiency. Therefore, the method is not used for an illumination drive requiring high image acquisition accuracy. The linear regulator is only applicable to a scenario of a low current or a scenario in which a forward voltage drop of an LED is slightly lower than a power supply voltage, but also has problems of low efficiency and a small input voltage range. A switching-type synchronous-buck drive has characteristics of flexible circuit topology, high efficiency, and a broad input voltage range, and has high current sampling accuracy. After factors such as working efficiency, an installation size, a static current, a working voltage, noise, and output regulation are comprehensively considered, currently, most of drive circuits of image illumination detection devices use switching converters. A topology structure of a switching converter includes a buck manner, a boost manner, a buck-boost manner, and the like. However, such a switching converter cannot well resolve the following five problems and a problem that lighting effects of an LED attenuate due to long-time working:
(1) A buck-boost function. When an input voltage or a voltage drop of an LED fluctuates, an output voltage is regulated, to satisfy a requirement that an output current is constant and ensure that the LED stably and reliably emits light.
(2) High power conversion efficiency. A circuit drive loss is lowered, energy consumption is reduced, a quantity of times of charging a storage battery is reduced, and a service life of a battery is prolonged.
(3) A brightness regulation function. When an exposure time of an imaging system needs to be regulated, a current may be regulated by using a pulse width modulation (PWM) signal.
(4) There is a complete protection circuit. Various protection measures need to be taken to ensure reliable working of the protection circuit and the LED. The protection measures are, for example, low-voltage latching, over-voltage protection, overheat protection, and output open-circuit or short-circuit protection.
(5) A good heat dissipation function. Because of thermal properties of the LED, a temperature is one of important factors that affect stable working of the LED. When working at night, the LED is in a state of being lit up for a long time. Therefore, a good heat dissipation function is necessary, to ensure a service life and reliable working of the LED.